Power transmission



Jan. 5, 1960 D. B. GARDINER POWER TRANSMISSION Filed Oct. 19, 1954 FIG.2

INVENTOR. DUNCAN B GARDINER ATTORNEY POWER TRANSMISSION Duncan B.Gardiner, Detroit, Mich., assignor to Vickers Incorporated, Detroit,Mich., a corporation of Michigan Application October 19, 1954, SerialNo. 463,1ll

12 Claims. (Cl. 103-136) This invention relates to power transmissions,and is particularly applicable 'to those of the type comprising two ormore fluid pressure energy translating devices, one of which mayfunction as a pump and another as a fluid motor.

The invention is concerned generally with rotary fluid energytranslating devices adapted for use in hydraulic power transmissionsystems and in particular to those of the sliding vane type.

A form of pump in the hydraulic power transmission field utilizes arotor having a plurality of spaced radial vanes rotatable therewith andslidable relative thereto in slots provided in the rotor. The rotor andvanes cooperate with a vane track in the'stator member which defines oneor more working chambers between the outer periphery of the rotor andthe vane track and through which the vanes pass carrying fluid from theinlet port to the outlet port.

The outer edges of the vanes are adapted to be kept in contact with thetrack and the spacing between adjacent vanes varies as the rotor turnsproducing a pumping action. As the rotor turns the vanes are extendedoutwardly by centrifugal force and are retracted inwardly by cam contouraction of the track during thepressure i A or discharge phase of thedevice. .On the discharge phase wear take up. A large amount of wear onthe ends of the vanes and to some extent on the cam trackcan take placewith only a' very slight effect on the efficiency of the pump. This isdue to the fact that the-vanes are maintained in contact with'the camtrack by centrifugal force and fluid pressure and that the pump actionis independent of how much the tips of the vanes have been worn oft".Although'a certain amount of wear is ennissible without destroying theefliciency of the pump, when certain limiting speeds and pressures andvolumetric capacities are exceeded the wear rate is so great as to beeconomically unfeasible. Thus one limiting factor in this design of pumphas been foundto be the rate'of:

wear between the outer edges of the vanes and the surface of the vanetrack under excessive operating conditions.

Because of the limitations of devices wherein outlet pressure iscontinuously conducted to the inner ends of the vanes, otherconstructions have been designed which connect the high pressure side ofthe device to theinner ends of the vanes only on the high pressure ordischarge phase thereof and which connect the low pressure or inlet sideof the device tothe inner ends of the vanes on the suction phase.Although it would appear that this would providepproperbalancingof'theinward and 2,919,651 Fatented Jan. 5, 1960 "ice 2 outwardpressures on the vanes' as they passed through the low and high pressureworking chambers of the device, this is not the case. At higherspeeds'the vanes become improperly balanced and not only is thevolumetric efliciency of the device decreased but likewise its pumpingcapacity. As the speed of the device increases the centrifugal forceurging the vanes against the track type.

It is another object of thisinvention to provide a fluid energytranslating device having an improved vane biasincreases but thisadvantage is overcome by an'increased pressure diiferential tending toseparate the vanes from the track. As the speed of the rotor increasesthe pressure difierential required to cause the vanes to pump the fluidout of the intervane spacesinto the delivery passage also increases andat certain higher speeds becomes so great that the vanes are unbalancedinwardly and move away from the track. I

Still other types of devices have been designed to provide a properunbalanced condition "to meet the requirements which utilize intricatevalving and portingand even auxiliary booster units.

It is therefore a general object of this invention to provide animproved low cost, eflicient and long wearing fluid energy translatingdevice, of the sliding vane ing arrangement.

It is still-another object ,of this invention to provide a fluid energytranslating device having' an improved vane structure and vane biasingarrangement which reduces wear and increases eflicien cy.

It is a further object of this invention to provide a rotary fluidenergy translating device incorporating sliding stepped vanes and apressure transmitting arrange ment to both ends and the stepped portionof the vanes which assures proper control of the vanes during the complete cycle at high pressure and high speeds and which reduces wear'andincreases volumetric efliciency. I

It is also an object of'this invention to provide a fluid energytranslating device incorporating radially sliding stepped vanes with apressure transmitting system associated therewith to produce acontrolled, safe and efiicient pressure differential thereon for urgingthe vanes in contact with the vane track.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferred form of the present invention is clearlyshown.

A In the drawing:

Figure 2 is a sectional view taken on line 2 2 of Figure 1.

Figure 3 is a sectional view taken on line 33"of Figure 1.

Figure 4 is an enlarged partial sectional view of the values asillustrated in Figure 2.

Referring now to Figure 1 there is shown a rotary fluid pump indicatedgenerally by the numeral 10, the

housing of which comprises a cam ring" section 12 sandwiched between abody section 14 having a wear plate 16 and an end cover 13, all of whichare suitably conneced to each other by bolts 20. The body section 14 isprovided with an inlet supply connection port 22 having an inlet passage24 leading therefrom which is branched and terminates in a pair of fluidopenings, one' of which is sho'wn in Figure 1, registering withduplicate opposed fluid openings 26 and 27 extending through the cover18 which leads directly from a pressure delivery chamber 38 formed in anenlarged bore 32 of the end cover 18 when a pressure plate 34 isfloatably mounted in the bo're 32. The pressure plate 3 2- and wearplate 16 are each formed with a fiat surface indicated, respectively, bythe numerals 36 and 38 which abut opposing flat faces 40 and 4-2 of thecam ring 12 and provide fluid sealing engagement for the immediatelyadjacent faces of a rotor 44 mounted within the cam ring 12. Thepressure plate is adapted to be urged against a portion of the flat face40 of the cam ring 12 and in fluid sealing engagement with the rotor bypressure in the pressure chamber. A spring 35 initially biases thepressure plate toward the rotor until pressure builds up in the pressurechamber.

The rotor 44 is driven by a shaft 46 provided with a seal 47, andextends from the body for connection to a prime mover, not shown. Theshaft is spline connected to the rotor at 48 and is rotatably mounted inbearings 58 and 52, mounted in the body 14. ring seals 54 and S6 preventleakage at the juncture of the end cover 18 and the wear plate 16 withthe cam ring 12 while an O ring seal 58 prevents leakage at the junctureof the body 14 and the wear plate 16.

The innersurface of the cam ring 12 forms a cam track substantiallyelliptical in shape, indicated by the numeral 60, against which theouter tips 62 of vanes 64, the latter of which are slidably mounted inslots 66 of the rotor 44, are adapted to be maintained in contact. Thecam track contour and the outer periphery of the rotor define twoopposed working chambers, indicated by the numerals 68 and 70, which forthe purposes of convenience, may be divided. into fluid inlet zones orfluid. delivery zones. The fluid inlet zo'nes are those portionsv of theworking chambers 68 and 70 registering with the opposed fluid inlet.openings 26 and 27 in the Wear plate 16. The fluid. delivery zones arethose p.0r-

tions of the working chambers 68 and 70 registering respectively withopposed arcuate fluid delivery ports 72 and 74 in the pressure plate 34,which are connected to the pressure chamber 30 by means of duplicatepassages 75 leading therefrom, one of which is shown in Figure 1.

The vane. track 60 includes an inlet zone ramp extending from a to b, atrue arc portion extending from b to c, a delivery zone ramp extendingfrom c to d, and another true are portion extending from d to e. Thetrack is symmetrical about both its major and minor axes, thus each ofthe ramp and. true are portions from a to e are duplicated in. the lowerportion of the track. As the ends of the vanes traverse the inlet ramps,the vanes mo've radially outward with respect to the rotor, and whilethe vane ends traverse the delivery ramps the vanes move radiallyinward. In the true are portions, the vanes partake of no radialmovement.

The inner ends of the vane slots 66 are enlarged to form, with the innerends 77 of the vanes 64, small enclosed undervane pressure chambers 78which undergo cyclic contraction and expansion during rotation of therotor. Each vane slot 66 is also formed with a stepped portion indicatedby the numeral 80 which, together with a step in each vane indicated bythe numeral 82, forms.

an enclosed intermediate pressure chamber 84 which remains enclosedwhile undergoing cyclic expansion and contraction as, the rotorrevolves.

In the form of device illustrated a flow path is formed connecting thehigh pressure side of the device to the intermediate chambers and whichalso interconnects the contracting and expanding intermediate chambers.The flow path is formed byproviding diametrically opposed po'rts 86 anddiametrically opposed ports 88 in the pressure plate, the former ofwhich are adjacent the inlet ramps and connected to the pressure chamber30 by drilled passages 90, while the latter ports 88 are adjacent theoutlet ramps. and. connected to the passages 75 which lead to thepressure chamber 39 by angular restriction passages indicated by thenumeral 92. The pressure chamber 30 thus forms with the pressure plateoutlet or delivery ports 72 and 74 and the passages 75 a continuousoutlet passage leading to the outlet port 28 and also forms with thediametrically opposed ports 86 and 88 a continuous flow path forconnecting the high pressure side of the device to the intermediatechambers and interconnecting the expanding and contracting intermediatechambers to each other. The vanes traversing the outlet ramp cd and itsduplicate outlet ramp are retracted. causing contraction of theirassociated intermediate chambers while simultaneously the vanestraversing the inlet ramp a-b and its duplicate inlet ramp are extendedcausing an expansion of their associated intermediate chambers. Theretracting vanes continuously push fluid out of their associatedintermediate chambers into the flow path simultaneously feeding theexpanding intermediate chambers of the vanes traversing the inlet ramps.

For the purpose of equalizing the pressure on the inner and outer endsof the vanes, the rotor is providedwith a plurality of angular drilledpassages 94", one for each vane slot, which leads from the peripheryoffthe rotor, between the vanes to the enlarged chambers 78' at theinner end of each vane slot. The outer end of'thejvanes are constructedwith a trailing taper 96 and a relatively smaller leading taper 98 toform the tips 62 of the vanes which contact the vane track. The outersurfaces of the vanes comprising the tapers 96 and 98 are exposed to thepressures in the expanding and contracting intervane spaces, and bymeans of the angular passages 94, the cyclically changing intervenepressure is conducted to the inner. chambers 78..

The restricted. passages 92, which connect the intermediate vanechambers to the pressure chamber passages 75 are adapted. to. create apressure in the intermediate stepped. vane chambers on the dischargephase of the device greater than the. pressure in the end chambers ofthe. vanes for producing a favorable unbalanced outward force thereon.The size of the restrictions and the effective area of the exposedsurface of the stepped portions of the vanes are preselected to create aresultant force sufficient to maintain thetips of the vanes in contactwith the vane track but low enough to prevent excessive ring wear. Inthe type of vane structure illustrated, the length of the smallertapered portion of the outer ends of the vanes, and the effective areaof the stepped 'portion of the vane, are also correlated and preselectedto provide at least a 2:1 ratio in favor of the stepped portion. of thevane. As the tip of the vane is about to enter the discharge portion ofthe ramp from the true are portion, only the smaller tapered portion ofthe vane is exposed to high pressure and the selected area ratio isadapted to insure contact of the vane tips against the vane track duringthis portion of the cycle.

The fluid inlet ports 26 and 27, which extend completely through thewear plate 16, are also duplicated respectively by ports 100 and 102 inthe face 36 of the pressure plate to produce proper filling and balanceon opposite sides of the. rotor. In order to facilitate filling of theundervane chambers during the suction stroke and during high. speedoperation,v the Wear plate is also provided, with auxiliaryv inlet ports1.04 and 106 which are connected to the inlet passages of the bodydevice by slots 1.081 and 114) in the wear plate. Duplicate auxiliaryinlet ports 112 and 114 are provided in the face of the pressure plateadjacent the rotor, which lead respectively by slots 11-6 and 118 to arecess 120 in the plate in alignment with the rotor shaft. Inlet fluidis conducted from the. auxiliary inlet porting in the wear plate side ofthe device through the medium of the spacing between the shaft androtor. splining to the recess and by means. of. the slots 116 and 118 inthe pressure plate to the. duplicate: auxiliary inlet ports 112 and. 114of the pressure plate. Dowel pins 122 are utilized to provide properalignment of the porting located in the wear and pressure plates withthe working chambers of the device;

In operation, as the rotor turns, fluid entering the inlet port isconducted by the branched inlet passage 24 and the openings thereof tothe arcuate inlet ports 26 and 27 of the wear plate to the fluid inletzones of the working chambers 68 and 70. Fluid is also conducted to theexpanding undervane chambers 78 from the fluid inlet zones by means ofthe angular rotor passages 94. Proper filling of the undervane chambersis insured by the auxiliary inlet ports 104 and 106 which are connectedto the branched inlet passage 24 through the slots 108 and 110 in thewear plate. Proper filling and rotor balancing is also facilitated bythe duplicate inlet ports 100 and 102 of the pressure plate registeringwith the working chambers 68 and 70 on the opposite side of the rotorand by the duplicate auxiliary undervane porting 112 and 114, also inthe pressure plate, which is connected to the splined rotor and shaftpassageway by the slots 116 and 118 in the pressure plate.

The displacement of the device is conducted from the fluid delivery zoneof the working chambers of the device through the delivery ports 72 and74 of the pressure plate to the pressure chamber 30 and thence by meansof outlet connection port 28 to a hydraulic system, not shown. As thevanes pass through the inlet and the outlet ramps of the vane track, thepressure at the extreme ends of the vanes is equalized. The resultantforce on the ends of the vanes, however, is unbalanced because of thedifferential end areas of the vanes. As the vanes pass through the inletzones across the inlet ramp at to b and the duplicate inlet ramp, theyare extended outwardly by centrifugal force, but engagement of the tipsof the vanes with the vane track is insured by a small force created onthe stepped portions of the vanes. This is accomplished'by transmittingpressure from the pressure chamber 30 through the drilled passages 90and the intermediate chamber pressure ports 86 of the pressure plate tothe intermediate vane chambers 84. The magnitude of the force, resultingfrom the transmittal of pressure to the preselected effective surfacearea of the stepped portions 82 of the vanes, is intended to besufficient for insuring contact of the tips 62 of the vanes 64 with thevane track 60, but of a proper value for minimizing the wear rate of thevane tips and vane track. In most cases, only a slight force isnecessary.

The pressure at the unbalanced end areas of the vanes which are passingthrough the delivery ramp is substantially equalized and if the samepressure were transmitted to the remaining balancing area of the steppedportion of the vanes, it would appear that because of the balanced areaconditions, centrifugal force alone would be suflicient to maintain thetips of the vanes in contact with the vane track. As previouslyexplained, however, the pressures existent at the ends of the vanes asthey pass across the delivery ramp are not completely equalized, and thepressure differential is in favor of urging the vanes from the track.This unfavorable condition is overcome by increasing the pressure in thecontracting intermediate vane chambers to a magnitude in excess ofoutlet pressure transmitted to the ends of the vanes. The pressure inthe intermediate vane chambers is increased by means of the restrictedpassages 92. Both the vane end chambers 78 and the intermediate chambers84 contract in size as the vanes pass across the delivery ramp cd, andthe duplicate delivery ramp. The fluid displaced from the intermediatechambers must pass through the restricted passages 92 to the outletpassages 75 in the pressure plate and thence to the pressure chamber 30which also serves to interconnect the contracting intermediate chamberswith the expanding intermediate chambers. The size of the restrictionsis thus preselected to, raise the pressure sufliciently in the inter- 6mediate vane chambers, when acting on a predetermined efiective area ofthe stepped portions of the vanes, for overcoming the slight pressuredifferential conditions existing on the outer ends of the vanes. Thepressure is adapted to be raised sufficiently to overcome the slightunbalanced conditions existing on the ends of the vanes in favor ofseparating the vanes from the vane track to a favorable unbalancedcondition insuring contact of the tips of the vanes with the vane track,but low enough to provide a favorable wear rate condition. The pressurevalue for the intermediate vane chambers may be selected for mostefiicient operation for any particular unit.

Devices embodying the invention operate at much higher pressures andspeeds than conventional devices of the type previously described. Thegreatly improved performance of the device is due to the stepped vanedesign with end and intermediate pressure chambers and the controllingof the pressure within one of the chambers, which is the intermediatechamber in the form of device illustrated. An unbalanced force iscreated by the design which tends to maintain the tips of the vanes incontact with the track during the complete cycle of the device and yetminimizes excessive wear rate while providing utmost efliciency and longlife.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. In a fluid pressure energy translating 'device of the sliding vanetype comprising a body including a track member and wherein one end ofeach vane abuts the track and the intervane spaces during a cycle of thedevice undergo alternate expansion and contraction phases, said bodyincluding an inlet and an outlet passage for conducting fluid to andfrom the intervane spaces, one of said passages being a low pressurepassage and the other of said passages being a high pressure passage,means forming two pressure chambers for each vane, each vane having twosurfaces, one in each chamber, both being effective under pressure insaid chambers to urge the vanes into engagement with the track, meansfor conducting the cyclically changing intervane pressure to only one ofsaid two chambers, passage means connecting the high pressure. passageto the other of said chambers during theintervane spaces expansionphase, and means forming a restricted flow path from the said other ofsaid chambers during the intervane spaces contraction phase for creatinga pressure in said other chamber during said phase greater than isexistent in the high pressure passage.

2. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps, and wherein the endsof the vanes abut the track and the intervane spaces undergo alternateexpansion and contraction as the vanes traverse the inlet and outletramps, said stator including an inlet and an outlet passage forconducting fluid to and from the intervane spaces, one of which is ahigh pressure passage and the other of which is a low pressure passage,the combination of a plurality of stepped vanes slidably mounted in aplurality of stepped slots in the rotor and forming two pressurechambers associated with each vane,

each vane having surfaces, one in each chamber, ef-

and means forming a restricted flow path from the other.-

of said two chambers as the vanes traverse the outlet "ramp for creatinga pressure in the said other chamber greater than in the high pressurepassage.

3. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps, and wherein the endsof the vanes abut the track and the intervane spaces undergo alternateexpansion and contraction as the vanes traverse the iniet and outletramps, said stator including an inlet and an outlet passage forconducting fluid to and from the intervane spaces, one of which is ahigh pressure passage and the other of which is a low pressure passage,the combination of a plurality of stepped vanes slidabiy mounted in aplurality of stepped slots in the rotor and forming two pressurechambers associated with each vane, each vane having surfaces, one ineach chamber, effective under pressure to urge the vanes into engagementwith the track, porting means for conducting the cyclically changingintervane pressure to only one of said two chambers, passage meansconnecting the high pressure passage to the other of said two chambersas the vanes.

traverse the inlet ramp, and means forming a restricted flow path fromthe other of said two chambers as the vanes traverse the outlet ramp andcreating a pressure in the said other chamber greater than in the highpressure passage.

4. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps, and wherein the endsof the vanes abut the track and the intervane spaces undergo alternateexpansion and contraction as the vanes traverse the inlet and outletramps, said stator including an inlet and an outlet passage forconducting fluid to and from the intervane spaces, one of which is ahigh pressure passage and the other of which is a low pressure passage,the combination of a plurality of stepped vanes slidably mounted in aplurality of stepped slots in the rotor and forming two enclosedpressure chambers associated with each Vane, each vane having surfaces,one in each chamber, effective under pressure to urge the vanes intoengagement with the track, porting means for conducting the cyclicallychanging intervane pressure to only one of said two chambers, andpassage means connecting the high pressure passage to the other of saidtwo chambers as the vanes traverse the inlet ramp and the outlet ramp.

5. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps which the outer endsof the vanes engage and causing during a cycle of the device alternateexpansion and contraction phases of the intervane spaces, said statorhaving inlet and outlet passages for conducting fluid to and from theintervane spaces, one of which is a low pressure passage and the other ahigh pressure passage, the combination of a plurality of stepped vanesslidably mounted in a plurality of stepped slots in the rotor andforming an end chamber and an intermediate chamber in each slot in whichan end surface and an intermediate surface of each vane are respectivelyeffective under pressure in said chambers to urge the outer ends of thevanes in engagement with the track, means for porting the cyclicallychanging intervane pressure to the inner chambers in timed relation withthe expansion and contraction phases of the intervane spaces, and meansforming a continuous flow path interconnecting the intermediate chambersof the vanes, traversing the inlet and outlet ramps and the highpressure passage.

6. In a fluid pressure energy translating device of the sliding vanetype comprising a body including a track having an inlet and an outletramp separated by a substantially true are section and wherein theintervane spaces during a cycle of the device undergo expansion andcontraction phases between the true are portion of the track, said bodyhaving inlet and outlet passages for conducting fluid to and fromintervane spaces one of which is a low pressure passage and the other ofwhich is high pressure passage, means forming an end chamber and anintermediate chamber for each vane, each vane having an end surface andan intermediate surface respectively in said chambers and effectiveunder pressure therein to urge the outer ends of the vanes in engagementwith the track, each vane having a leading and a trailing surface onopposite sides of the track engaging outer end of the vane, which areexposed to pressures in the intervane spaces as the vanes traverse thetrack ramps, the effective area of the vane intermediate surface beingat least twice that of the effective area of the leading surface thepressure on which tends to separate the vane from the track, means forconducting the cyclically changing intervane pressure to one of said twochambers, and passage means interconnecting the high pressure passageand each of the other of said two cham bers to each other during theexpansion and contraction phases of the intervane spaces.

7. In a fluid energy translating device of the slidingvane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps, and wherein the endsof the vanes abut the track and the intervane spaces undergo alternateexpansion and contraction as the vanes traverse the inlet and outletramps, said stator including an inlet and an outlet passage forconducting fluid to and from the intervane spaces, one of which is ahigh pressure passage and the other of which is a low pressure passage,the combination of a plurality of stepped vanes slida'oly mounted in aplurality of stepped slots in the rotor and forming two enclosedpressure chambers associated with each vane which remain enclosed as theintervane spaces expand and contract, each vane having surfaces, one ineach chamber, effective under pressure to urge the vanes into engagementwith the track, porting means for conducting the cyclically changingintervane pressure to only one of said two chambers, and means forming acontinuous flow path interconnecting the high pressure passage and eachof the other said chambers to each other, as the vanes traverse theinlet and the outlet ramps.

8. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps which the outer endsof the vanes engage and causing alternate expansion and contractionphasesof the intervane spaces, said stator having inlet and outletpassages for conducting fluid to and from the intervane spaces, one ofwhich is a low pressure passage and the other a high pressure passage,the combination of a plurality of stepped vanes slidably mounted in aplurality of stepped slots in the rotor and forming an end chamber andan intermediate chamber in each slot in which an end surface and anintermediate surface of each vane are respectively effective underpressure in said chambersto urge the outer ends of the vanes inengagement with the track, means for porting the cyclically changingintervane pressure to the end chambers in timed relation with theexpansion and contraction phases of the intervane spaces, and meansconnecting the high pressure passage to the intermediate chambers duringthe intervaneexpansion and contraction phases of the device.

9. In a fluid pressure energy translating device of the sliding vanetype comprising a body including a track member and wherein one end ofeach vane abuts the track and the intervane spaces during a cycle of thedevice undergo alternate expansion and contraction phases, said bodyincluding an inlet and an outlet passage for conducting fluid to andfrom the intervane spaces, one of said passages being a low pressurepassage and the other of said passages being a high pressure passage,means forming two pressure chambers for each vane, each vane having twosurfaces, one in each chamber, both being eifective under pressure insaid chambers to" urge the" vanes into engagement with the track, meansfor connecting in timed relation the cyclically expanding andcontracting intervane spaces to one of said two chambers, passage meansconnecting the high pressure passage to the other of said chambersduring the intervane spaces expansion phase, and means forming arestricted fiow path from one of the said two chambers during theintervane spaces contraction phase for creating a pressure in the saidone of said two chambers during said phase greater than is existent inthe high pressure passage.

10. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps, and wherein the endsof the vanes abut the track and the intervane spaces undergo alternateexpansion and contraction as the vanes traverse the inlet and outletramps, said stator including an inlet and an outlet passage forconducting fluid to and from the intervane spaces, one of which is ahigh pressure passage and the other of which is a low pressure passage,the combination of a plurality of stepped vanes slidably mounted in aplurality of stepped slots in the rotor and forming two enclosedpressure chambers associated with each vane which remain enclosed as theintervane spaces expand and contract, each vane having surfaces, one ineach chamber, etfective under pressure to urge the vanes into engagementwith the track, porting means for connecting the cyclically expandingand contracting intervane spaces to only one of said two chambers, meansconnecting the other of said two chambers to the high pressure passageas the vanes traverse the inlet ramp, and means forming a restrictedflow path from one of said two chambers as the vanes traverse the outletramp for creating in said chamber, as the vanes traverse said ramp, acontrolled pressure greater than is existent in the high pressurepassage.

11. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps which the outer endsof the vanes engage and causing alternate expansion and contractionphases of the intervane spaces, said stator having inlet and outletpassages for conducting fluid to and from the intervane spaces, one ofwhich is a low pressure passage and the other a high pressure passage,the combination of a plurality of stepped vanes slidably mounted in aplurality of stepped slots in the rotor and forming an end chamber andan intermediate chamber in each slot in which an end surface and anintermediate surface of each vane are respectively effective underpressure in said chambers to urge the outer ends of the vanes inengagement with the track, means for connecting the cyclically changingintervane spaces to the end chambers in timed relation with theexpansion and contraction phases of the intervane spaces, passage meansconnecting the high pressure passage to the intermediate chambers duringthe intervane spaces contraction phase, and means forming a restrictedflow path from one of said chambers during the intervane spacescontraction phase for creating a controlled pressure in the said one ofsaid two chambers during said phase greater than is existent in the highpressure passage.

12. In a fluid energy translating device of the sliding vane typecomprising a stator having a rotor rotatably mounted therein anddefining a vane track with inlet and outlet ramps which the outer endsof the vanes engage and causing alternate expansion and contractionphases of the intervane spaces, said stator having inlet and outletpassages for conducting fluid to and from the intervane spaces, one ofwhich is a low pressure passage and the other a high pressure passage,the combination of a plurality of stepped vanes slidably mounted in aplurality of stepped slots in the rotor and forming an end chamber andan intermediate chamber in each slot in which an end surface and anintermediate surface of each vane are respectively efiective underpressure in said chambers to urge the outer ends of the vanes inengagement with the track, means for connecting the intervane spaces tothe end chambers in timed relation with the expansion and contractionphases of the intervane spaces, passage means connecting the highpressure passage to the intermediate chambers during the intervanespaces expansion and contraction phase, and means forming a restrictedflow path from the intermediate chambers during the intervane spacescontraction phase for creating a pressure in the said chambers duringsaid phase greater than is existent in the high pressure passage.

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